1. Field of the Invention
The present invention relates to an electronic unit and electronic apparatus provided with a substrate that includes electronic components, and particularly relates to an electronic unit and electronic apparatus in which it is difficult to disrupt the electric connections between wires and electronic components mounted on the substrate even under the application of an external force.
2. Description of Related Art
Electronic apparatuses such as computers, television receivers, and recording/reproducing apparatuses that record to and play back from disks and the like are provided with substrates on which electronic components are mounted. As an example of such an electronic apparatus, JP 2006-120378A (referred to as “Patent Document 1” hereinafter) discloses the configuration of an intercom provided with a substrate on which electronic components are mounted.
FIG. 7 illustrates a cross-sectional view of this conventional electronic apparatus. As shown in FIG. 7, an intercom 101, which is an example of an electronic apparatus, includes an outer housing 108 that encloses the apparatus. A substrate 102, on which an electronic component 103 is mounted, is contained within the housing 108. Terminals 104 of the electronic component 103 are electrically connected to the wiring (not shown) of the substrate 102. Bosses 105 are formed in the housing 108, and the substrate 102 is anchored to the housing 108 by threading screws 107 through the substrate 102 and into the bosses 105.
In recent years, weight reduction and miniaturization have been progressing in electronic devices, and the portability thereof is improving, as exemplified by laptop computers, mobile telephone terminals, portable game devices, and so on. Electronic devices that feature such portability are more likely to, for example, be dropped on the floor, collide with other objects, and so on, and thus it is necessary to shock-proof such devices.
FIG. 8 illustrates a perspective view of a conventional electronic apparatus 111 that has been shock-proofed. FIG. 9 illustrates a cross-sectional view taken along the C-C line shown in FIG. 8. FIG. 9 is a cross-sectional view of a substrate 116 that has been cut vertically relative to its main surface.
As shown in FIG. 9, a housing 112 contains an intermediate chassis 114. The intermediate chassis 114 is anchored to the housing 112 via support portions 113. The intermediate chassis 114 is formed of metal, and bosses 115 are formed on the inner surface of the intermediate chassis 114. The substrate 116 is anchored to the bosses 115 with screws 117. An electronic component 118 is mounted on the substrate 116. Terminals 118a of the electronic component are connected to a wiring pattern 116a provided on the surface of the substrate 116. Recently, taking into consideration high-density mounting and space conservation, components packaged as ball grid arrays (BGAs) are used as the electronic component 118. Furthermore, the rear surface of the mounting surface of the electronic component 118 is in contact with the intermediate chassis 114 via a buffer member 118b formed of a material that has a high degree of thermal conductivity, such as graphite.
According to the electronic apparatus shown in FIG. 9, heat generated by the electronic component 118 can be dissipated to the intermediate chassis 114 via the buffer member 118b formed of a material that has a high degree of thermal conductivity, thereby improving the efficiency of heat dissipation of the electronic component 118. Furthermore, electromagnetic waves emitted by the electronic component 118 are absorbed by the intermediate chassis 114, making it possible to reduce electromagnetic waves leaking to the exterior of the electronic apparatus.
If an impact is applied to such a conventional electronic apparatus, such as when the apparatus is dropped accidentally, the impact on the housing 112 will pass through the support portion 113 and the intermediate chassis 114 to the substrate 116. Because both ends of the substrate 116 are anchored to the bosses 115 using the screws 117, when a force such as an impact is applied, the substrate 116 experiences a wave and distorts, as shown in FIG. 10. When the substrate 116 distorts, there is a high probability that the terminals 118a of the electronic component 118 mounted upon the substrate 116 will separate from the wiring pattern 116a formed on the surface of the substrate 116, disrupting the electrical connection. Although such separation of terminals from the wiring pattern occurs more prominently in electronic components packaged as BGAs, there is also the chance for such a disconnection to occur in electronic components whose terminals are connected using connection wiring provided by QFPs (Quad Flat Packages).